1. Field of the Invention
The present invention relates to a sheet-bundle spine treatment apparatus for processing a spine of a folded sheet-bundle, and in particular relates to a sheet-bundle spine treatment apparatus having a crease adjusting function of pinching the spine and a back-flattening function of pushing the back of the spine, a sheet-bundle treatment apparatus including the sheet-bundle spine treatment apparatus, and an image-forming apparatus including the same.
2. Description of the Related Art
Conventionally, the folding of about 20 or less sheets in a seaming/folding device as a folding unit results in booklets. Sheet-bundles folded by the seaming/folding device in such a manner include a simple folded sheet-bundle, a folded sheet-bundle stitched by saddle stitching, and a folded sheet-bundle bound by perfect binding (not with a thread or staple but with an adhesive).
However, since the sheet-bundles have elasticity to some extent, as shown in FIG. 22, the folded product has a U-shaped curved bow adjacent to a spine (folding apex, backbone) Sb. When such sheet-bundles S are stacked, they will not lie flat so that it is difficult to store and transport them in a stacked state.
In order to stack such folded sheet-bundles S flat, a sheet-bundle spine treatment apparatus has been proposed in that the sheet-bundles S are flattened by reducing the bow of the spine Sb as shown in FIG. 8 (see Japanese Patent Laid-Open No. 2001-260564, corresponding to U.S. Pat. No. 6,692,208).
A conventional sheet-bundle spine treatment apparatus is shown in FIGS. 23 to 25. First, in the sheet-bundle spine treatment apparatus 901, the booklet saddle-stitched sheet-bundle S discharged from a folding roller pair 907 in an arrow B direction with the spine Sb in the lead is once stopped by an elevatable stop plate 905 (FIG. 24A). Then, the sheet-bundle spine treatment apparatus 901 grips the sheet-bundle S with gripping members 902 and 903 while elevating the stop plate 905 (FIG. 24B). At this time, the spine Sb protrudes from between the gripping members 902 and 903, while the stop plate 905 separates from the spine Sb. A pressure roller 904 serving as a spine treatment unit presses the spine Sb so as to proceed along the spine Sb in the arrow A direction. Thereby, the curved spine Sb is flattened by being pushed by the pressure roller 904 (see FIG. 25). Finally, the sheet-bundle spine treatment apparatus 901 discharges the treated sheet-bundle S by a discharge belt pair 906 in the arrow B direction into a discharge tray 908 to be stacked (FIG. 24C).
In addition, the conventional sheet-bundle spine treatment apparatus 901 may further serve as a sheet-bundle treatment apparatus so as to flatten the spine of the sheet-bundle folded by a sheet-bundle folder.
Furthermore, the conventional sheet-bundle spine treatment apparatus 901 constituted in the sheet-bundle treatment apparatus may also be incorporated in an image-forming apparatus for forming images on a sheet.
Another conventional sheet-bundle spine treatment apparatus is provided in that the spine folded by a first folding roller pair is pinched between a second folding roller pair different from the first one so as to adjust the shape of a spine crease. During the operation of the second folding roller pair, the first folding roller pair fixedly holds the sheet-bundle (see Japanese Patent Laid-Open No. 2003-182928).
However, in these conventional sheet-bundle spine treatment apparatuses, flattening the spine of the sheet-bundle is performed separately from fortifying the spine. Therefore, an apparatus has been expected to selectively perform flattening the spine of the sheet-bundle and fortifying the spine in one sheet-bundle spine treatment apparatus.
Also, a sheet-bundle treatment apparatus and an image-forming apparatus having such a sheet-bundle spine treatment apparatus have not been easy to use.